1. Field of the Invention
The present invention relates to a powered strength trainer, in particular to a DC or brushless motor having a linear relation between current and torque to replace a traditional iron weight plate as a load element, and also having a vibration training function for controlling a curved load, compensating a load current, and preventing a rewound steel wire from falling off.
2. Description of the Related Art
Regardless of recreation, health or professional reasons, fitness exercise is an important part of our life. For example, strength trainers become very popular in developed countries in Europe and America, and iron weight plates are used to build up muscles, promote physiological functions, and maintaining a good health. Thus the iron weight plate is called a “weight strength trainer”, whose structure is shown in FIG. 1. Such conventional strength trainer 10 is a weight machine that uses an iron weight plate 11 as a load of exercise, and patents of this sort were disclosed in U.S. Pat. Nos. 7,029,427, 5,833,585 and 4,478,411. However, the conventional loading methods still have the following shortcomings:
1. The iron weight plate 11 comes with a large volume and occupies much space. If a user needs to adjust the exercise load by increasing or decreasing the number and the weight of the load such as the iron weight plate 11, it will take much time and effort for the user to make the adjustment, and the user also has to stop the exercise to do so, and thus it is difficult to achieve the expected exercising effect.
2. The load such as the iron weight plate 11 is heavy and cannot be adjusted easily. Furthermore, an expected load acting as an index of the exercise cannot be achieved, and thus the exercising effect will be reduced substantially.
3. If the load such as the iron weight plate 11 is lifted by a transmission cable 12 and then released slowly, an annoying sound will be produced, and the irritating sound will cause discomfort to the exerciser.
4. The conventional strength trainer 10 is a weight load, and thus the load cannot be changed by setting an exercise curve, or vibration training cannot be preformed. As a result, the exercising function is limited.
5. Since the load cannot be adjusted during an exercise, such as the heartbeat rate exceeds a user's safe range, the load cannot be reduced automatically and immediately, and thus an over-exercise or exercise injury may occur easily.
Obviously, the conventional load device of the strength trainer 10 still has the following shortcomings and requires improvements.
In view of the aforementioned shortcomings of the prior art, the inventor of the present invention has provided an automatic load device for electric fitness equipments as disclosed in R.O.C. Pat. Publication No. 230359, wherein the torque of a DC motor is used to drive a steel wire to produce a rated tension in order to replace the conventional iron weight plates, and related technologies are disclosed in U.S. Pat. Nos. 5,020,794, 5,180,348, 4,979,733 and 4,678,184. However, the aforementioned prior arts still have the following drawbacks:
1. For a low load, the torque outputted by a DC motor is very low. Since the mechanical system inertia and mechanical loss offset a portion of the torque, the steel wire has no force exerted thereon and a very slow rewind speed. Thus, the speed is slower than that of the conventional iron weight plate, and users generally have poor response to the machines of this sort, and it is a pity of losing the original intention of exercises.
2. If there is a power disconnection or failure of the system when an exerciser is doing exercise, then the motor will lose its rewind capability, and the steel wire will be loosened. Thus, the steel wire will be slid from the spiral groove of the winch.
3. Due to the mechanical loss, the system inertia, and the acceleration of the transmission in the machine, the linear speed of the steel wire cannot match up with the user's exercise synchronously, and thus the machine of this sort is not good enough.
In view of the aforementioned issues, the inventor of the present invention provides a better solution and an improved design to overcome the shortcomings of the prior art and gives a better application to users.